Wire-wound brake drum or disc



July 22, 1958 Y M. G. WHITFIELD-v WIRE-WOUND BRAKE DRUM OR DISC FiledMarch 51. 1955 I AFTER FUSION BEFORE FUSION v INVEYNTOR MARSHALL G.WHlTFIELD United States Paton-t WlRE-WOUNDBRAKEDRUM 0R DISC Marshall G.'Whitfield, GardentCity, N .1 Y

ApplicationiMar'ch 31, '1955, SeriaINO. 498,150

3Claims. v(Cl. 188-218) This invention relates to composite metalbrakesof the drum or.disc type and, more particularly,tol brake drums or discscapable of dissipatinglarge.amounts of heat without attendantdeformation.

In conventional brake drumsemployed in association with internalexpandingbrakes, externallytdisposed'fins are often,pro'vided 'to assistindissipating the frictional heat generatedduring'br'aking. In manyinstances, heat dissipation from fins attached to the'drumisnot-entirely satisfactory-due in part .to mechanical. weakness of themeans for "fastening the;fin to the drumand, in part, ,to theaccumulation of road .dirt between the fins. These disadvantages havebeen sought to 'be avoided by casting a portion of thebrake'flange on aplurality of endless steel Wire hoops. But the manufacture of'this typeof drum does not entirely avoid theuseof fins and such construction iscos'tly and time-consuming, not only requiring the careful placing of aseries-of steel wire hoops in a-mold, but also the casting of moltenironundercarefully controlled conditions so asnot to displace'the'hoops.During use, the high-frictional temperatures'developed have a-tendencyto loosen the hoops, and their use is of little valueinsofar asheat-dissipating and 'flange-strengthening characteristics areconcerned.

It is,-therefore, an important object of this invention to provide aninexpensive composite metal wire-wound brake drum ordisc of-improvedstrength-which is capable of dissipating or of receiving and storinglarge quantities of heat without substantial deformation.

Another object of this invention is to provide a relatively light-weightcomposite-metal brake drum or disc capable of resisting deformation,under heavy-duty .conditions, such drum having one or more plies of. ahighstreng'th wire, having a coating-of a highlyheat-conductive-metal,-tension wrapped about and metallurgically bonded to the external surfaceof the drum onto an internalsurface of the disc.

By the term "*metallurgically bonded is meant that a portion of thefusedmeta'l 'of the coating'on' oneturn .of wire bonds itself to thecoating of another turn .and so on. Coating metal on the turns adjacentto'the surface of the drum is bonded both to the drum and'to adjacentturns, thus forming a *highly heat-conductive metal matrix. Preferably,the metal coating on the wire core is either copper or aluminum or analloy containing copper or aluminum, and such coating, when subsequentlyfused and bonded withthe ferrous metal of the drum, forms the desiredheat-conductive metal matrix. This matrix is capableof receiving largequantities of heat from the drum, storing this heat'brieflyand thendissipating it without injury :to the drum.

Another object of the invention is to provide a relatively light-weightcomposite metal brake drum composed of -aferrous metal drumhaving ribsor fins on its external circumferential surface and a number of turns ofa heatconductive ;metal=coated'ferrous wire wrapped between the ribsporeven overthe ribs; the metal coating. on the .2 wires being subsequentlyfused: to form a continuous heatconductive .matrix which.metallurgically .bonds the wires in situ with oneanother and with themetal of the drum.

An additional object. of the invention is to provide a strong,light-weight vdisctype of brake composed of at leastonecircular-flangeof .ferrousmetal, one surface of the flange being.adapted toengage a brake-shoe, and the opposite face being .incontactwitha number ofturns of a steel wire having. a highly heat-conductivemetal coating; 'such coating being subsequently fusedto form acontinuous heatfconductive matrix which metallurgically bonds the wirestogether and toth'e .fiange-onflanges-of the disc brake.

Yet another object .ofithe .invention .is eto provide a novel method ofmanufacturing a wire-wound brake drum which is easy and inexpensive-.tov perform. Themethod comprisesitightly wrappingthe external .surfaceof a ferrous-metal drum with a wire having a highly heat-conductivemetal coating anda core. preferably of steel or high strength alloysteel or rn'olybdenum. 'I-hecoating metal on the core is ,preferablycopper or aluminum, but-magnesium may also be used. The wound drum isthen subjected .to aheating operation at .an elevated temperature tofus'ethe coating,'but.at-.a temperature below the fusing point of thewire core and the ferrous metal brake drum. The metal forming thecoating. on the core of the wire is thus fused and'is permitted 'to'flowinsuch .a manner as tofill the interstitial spaces .between ..the wires.The molten metal also 'wets the surfaceof .the iron drum and forms'ithedesired metallurgical bond therewith. The steel core of the wire and/thesurface of-the irondrum are thus integrally unitedby aihighly.heat-conductive metal matrix.

Examination of the heatet'reateddrum reveals the formation ofacontinuousmetal matrix of coating material metallurgicallybonded toboth the wire and theperipheral heat-dissipating surface of the drum.This matrix afiords a highly efiicient heat-storing reservoir aswell asa path for facilitating Zthe dispersion of heat awayfrom'the surface ofthe 'brake drum, to the outermost part of thewire winding.

The above objects, as wellas other features of the inventionywillbe'ma'de more apparentas the description proceedsfe'specially whenconsidered in connection with the accompanying drawing, wherein:

Fig. '1 is a partial sectional elevational view of a' wirewoundbrake"drum embodying the principles of the present invention; and

FigDZ is'an er1larged' sectional view of thebrake drum shown in -Fig. 1,showing 'the relation of the elements before and afterfusion; I 1

Fi'gIS' is a partiahsectional view of a .disc brake embodying-theprinciples' of ,this invention; and

Fig.' 4=is a partialsectiona'l view of a drum having ridges or fins o'nthe externalsur'face thereof and covered with turns 'of'metal 'coate'dwire which are metallurgically bondedtothedrum.

In Fig. l is shown a conventionally castiron or .steel brake drum 10"having a cylindrical drum flange l1 integrally joined at one end thereofwit-hacircular backing plate '12 which is provided 'with a conventionalcentral axle receiving aperture and a series of circularly spacedbolt'holes to permitthe drum 10 to be.secured to anaxle assembly (notshown). The other end .ofthe cylindrical flange 11 may or may not beprovided with an annular lip l4 extending generally in a radiallyoutward direction.

The .present invention resides in means for promoting or facilitatingthe ,transmissionofuheat away from the peripheral surfaceoftthe flange1-1 of the' brake drum and, if necessary, storing. thisheatzbriefly'until it "can be safely dissipated. .For .this-purpose,-.;the :outer surface of the flange 11 is provided with anumber of turns of a composite wire which is tension Wound thereabout,the wire 20 defining interstitial spaces 21 therebetween. In accordancewith this invention, the composite wire 20 includes a high-tensilestrength steel or alloy steel or molybdenum core 22 which is providedwith a coating of one or more layers of a metal 24 having a relativelylow fusing temperature and a high heat conductivity and which is capableof forming a metallurgical bond with the wire and drum. Aluminum,copper, or magnesium or alloys thereof are examples of suitable coatingmetals which preferably are used in the practice of this invention. Anynumber ofturns of composite wire may be applied to the outer cylindricalflange of the brake drum. In the modification shown, two superimposedrows of wire are used, although a larger or smaller number of rows maybe used, if desired. A thinner wire 26 composed only of the coatingmetal may, if desired, be wound between the plies of wire to insurefreedom from porosity after the wound structure has been heated to thefusing temperature of the coating metal.

As shown in Fig. 3, the disc brake comprises a circular flanged steel oriron disc 30 having spaced flanges 32, the outer surfaces of which areadapted to engage a brake shoe. If desired, the brake disc may compriseone or a plurality of flange elements, but for purposes of illustration,two flanges are shown. The internal space between the flanges may bepartially or completely filled with tenion-wrapped ferrous or molybdenummetal wire 34 having a copper, aluminum or magnesium coating. When thewrapped disc is heated to a temperature above the fusing temperature ofthe metal coating, the latter fuses and forms a metallurgical bondingmatrix uniting the wires and flanges into an integral structure.

In Fig. 4, the ferrous metal drum is provided with a plurality of ridgesor fins 42 on the flange 41 thereof. The coated wire is then woundbetween the ridges and after fusion, the core 22 of the wire isintegrally bonded in the matrix 24 in the same manner as previouslydescribed in connection with Fig. 1.

Manufacture of the brake drum of the present invention may beaccomplished in the following manner. The external surface of the castiron or steel flange 11 is suitably cleaned, as by wire brushing,pickling or sand blasting, to provide a clean surface capable of forminga metallurgical bond with the metal coating of the composite wire. Aftercleaning, the surface of the drum may be coated with a thin layer 16 ofthe same or different metal as that used for the coating on the wire. Ifa different metal is used, it is one promoting the formation of adurable bond, e. g. tin or mloybdenum, when an aluminum-coated steelwire is used. The outer peripheral surface of the drum is then tightlyWound with one or more layers of the composite wire for a desired numberof turns in order to cover the outer surface of the ferrous metal flangepartially or completely. Thereafter, the thus wound drum is subjected toa heating operation carried out under suitable conditions to cause themetal coating on the wire to fuse and to fill substantially theinterstitial spaces between adjacent turns and plies of wire. Ifdesired, a thin wire of the same metal as used on the coating of thethicker steel or molybdenum core wire may be wound between the turns ofsuch wire, whereby on fusing, a porosity-free metal matrix is formedwhich provides a path for the rapid conduction of heat away from theferrous metal drum. Subsequent cooling of the drum causesre-solidification of the fused coating which, in effect, forms a strongintegral metallic structure between the wire core and the brake drumflange, such bonding matrix providing a lowresistance pathway for thedissipation of frictional heat.

Preferably, the steel or cast iron drum, after cleaning, may be coatedwith copper or aluminum to a thickness up to 5 mils. If desired,.asuitable fluxing or brazing compound may be coated on the copper coatingto promote the formation of a metallurgical bond with the coppercoating.

on the wires. When using aluminum-coated wire, it is desirable to coatthe iron base with a film of molybdenum or tin, thereby forming with thealuminum a complex molybdenum-iron-aluminum alloy or a complextin-ironaluminum alloy. This complex alloy is extremely tough anddurable and securely anchors the aluminum matrix to the drum.

Wrapping is preferably carried out by rotating the drum and puttingsufiicient drag or tension on the wire so as to generate considerablecompressive force in the flange of the drum. This compressive forcecounteracts the expansive force developed in the drum during normal orheavy-duty braking. In general, during wrapping, the wire is appliedwith a drag of between 5 and pounds and preferably between 10 and 25pounds depending on the diameter of the drum and thickness of the wire.The

wire may be close-Wound or one turn may be spaced from another turn by adistance not substantially greater than the diameter of the wire.However, in a preferred embodiment of the invention, the wire isclose-wound,

and the thickness of the copper or aluminum coating is suflicient toprovide sufficient copper or aluminum substantially to fill theinterstices between the wires after the wrapped drum is heated to atemperature sufficiently high to cause the copper or aluminum to meltand flow.

As shown in Fig. 2, the wires are closely wound on the drum 11 which ispreferably precoated with a layer 16 of copper, if a copper-coated steelwire is employed, or with a layer of aluminum, if an aluminum-coatedsteel wire is employed. It is essential that the thickness of the metallayer 16 and the thickness of the coating on the steel wire be capableof providing suflicient metal to form a bonding metal matrix in whichthe core of the wire is embedded. In Fig. 2, the relative position ofthe wire wrapping is shown after fusion. Some of the metal of layer 16has alloyed itself with the iron base 11, and the 'steelcore 22 of thewire is firmly embedded in the copper or aluminum matrix. In the eventthat an insuflicient amount of copper, or aluminum, is provided by thecoating or layer 16, then a thin copper, or aluminum wire 26 may besimultaneously wound with the coated wire. This additional wire is of adiameter which will substantially fill the space between the coatedwires.

As a feature of the present invention, brake flanges of reducedthickness may be used in conjunction with the rows of composite wireturns, the tension of the composite wire being amply sufiicient toreinforce and prevent distortion of the shell flange during use.

The coating surrounding the core should be of sufficient thickness toprovide sufficient material to eliminate conductive resistance to theflow of heat where the composite wires are in point or line contact witheach other or the brake flange. Preferably, the coating should besufficiently thick to provide enough material to fill the interstitialspaces, but additional filler stock may be added when indicated by costconsiderations Small diameter core wires are preferred because they formsmaller interstitial spaces.

From the above, it will be seen that the brake drum or brake discs ofthe present invention are admirably suitable for heavy-duty heatdissipation purposes. The metal coating of the composite wire is fusedand then solidified to form a metallurgical matrix integrally bondingthe brake flange and the steel Wire core. At the same time, it affords ahighly efiicient pathway for receiving or storing frictional heatdeveloped when a brake shoe is applied to the surface of the brake drum.This matrix forms an excellent transition zone in light weight metaldrums which helps to relieve bonding strains in the structure. The brakedrum or disc of the present invention is light and sturdy since thebrake flange may be relatively thin, yet it is not easily fractured ordistorted.

It is to be understood that modified variations may be efiected withoutdeparting from the scope of the novel concepts of the present invention.

What is claimed is:

1. A fin-free wire-wound brake drum comprising a ferrous metal flangehaving an inner surface for contacting a brake shoe, a heat-conductivemetal matrix comprising a metal selected from the groupconsisting ofcopper, aluminum and magnesium metallurgically bonded to and extendinguniformly over the entire peripheral exterior surface of said flange,and a plurality of plies of a high-tensile wire selected from the groupconsisting of steel, high strength alloy steel and molybdenum wrappedabout the entire exterior peripheral surface of said flange, each turnof said wire being spaced from an adjacent turn solely by said matrixand metallurgically bonded with and completely encased in said matrix.

2. In a fin-free brake drum comprising a ferrous metal cylindricalflange having one edge thereof integrally formed with a nadial backingplate and the opposite edge thereof integrally formed with a radiallyand outwardly extending lip, the improvement comprising a plurality ofuninterrupted plies of tension-wrapped wire selected from the groupconsisting of steel, high strength alloy steel and molybdenum wrappedaround and extending uniformly over substantially the entire peripheralouter surface of said cylindrical flange from a point adjacent to thebacking plate to a point adjacent to the lip, said wire having a coatingof a heat-conductive metal selected from the group cosisting of copper,aluminum and magnesium, said plies being disposed with the coating ofone turn of wire in contact with the coating of an adjacent turn of wireand wound one upon the other to a height substantially equal to theheight of said lip and a matrix formed by the fusion of said coating onsaid wire metallurgically bonding the individual turns of each of saidplies together and to said outer surface of said flange.

3. In a fin-free brake drum including a radially extending portion and acylindrical flange portion integral with the perimeter of said radiallyextending portion, said cylindrical flange portion having parallel wallsof uniform thickness throughout insuflicient to withstand 6 brakingpressure applied to the internal wall surface of said flange, theimprovement comprising at least one continuous and uninterrupted ply ofwire selected from the group consisting of steel, high strength alloysteel and molybdenum having a coating of a heat-conductive metalselected from the group consisting of copper, aluminum and magnesium,said wire being wrapped with the coating of one turn of the wire of suchwrap, in contact .With the coating of an adjacent turn of said Wire andsubstantially completely covering the entire external peripheral wallsurface of said cylindrical flange, the combined thickness of the wireand flange providing suificient metal thickness to withstand the brakingpressures to which the internal wall surface is subjected, and a matrixof a heat-conductive metal formed solely by the fusion of said coatingon said wire, metallurgically bonding said wire to the external wallsurface of said flange, said matrix forming a pathway between said wirefor receiving and storing frictional heat developed by brake pressureapplied against the internal wall surface of said flange.

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